The invention relates to circuit arrangements for the determination of the direction of received wave energy, particularly sound waves, with the use of a ranging system having two perpendicularly arranged pairs of dipoles including individual receivers, and a measuring device with a bearing display device for displaying the direction of impingement of the received wave energy in the plane of the ranging system.
Ranging systems of the above type are known and are usually used as gradient ranging systems. In such systems, each pair of dipoles includes two oppositely disposed individual receivers or a hollow cylindrical receiving element of piezo-ceramic or magnetostrictive metal. These receivers are connected with circuitry for measuring the direction of impingement of the received energy wave which direction is then connected to a display device.
Systems for evaluating and producing a display of the direction of impingement of received energy waves are known. The circuitry of the known systems produces this display by forming the simple difference of the received signals of the individual receivers of each pair of dipoles, and the sum of the received signals of all of the individual receivers. The two signals representing differences are fed to the deflection system of the display device and the signal representing the summation is first phase shifted and then applied to the brightness control of the display device. A system operating in this manner is shown in the U.S. Pat. No. 3,496,527 . The display device generally utilized for such purposes is a cathode-ray tube.
Instead of utilizing the summation signal, it is also possible to use the received signal of an additional panoramic or omnidirectional receiver which is arranged in the center of the four individual receivers corresponding to the two pairs of dipoles. In either case, the direction of impingement of the received wave energy is displayed in the form of a radial luminous streak whose position with respect to a reference direction indicates the direction of impingement.
It is also known that by means of a correlation process between the differences derived from the received signals from the individual receivers of a pair of dipoles and the received signal from the panoramic or omnidirectional receiver whose output is independent of the direction of impingment, a display of the direction of impingement can be developed in the form of a luminous dot or streak on the screen of a cathode-ray tube. The distance of the luminous dot from the center of the screen or the length of the luminous streak can be variably controlled by an adjustable amplification of the signal representing the difference between the received signals (see U.S. Pat. No. 3,496,527 ).
In gradient ranging systems in which the received signals are used for the indication of the direction of impingement as differences which are evaluated either directly or correlatively, systematic ranging errors which occur due to higher harmonics of the angle of impingement of the wave energy with respect to a reference direction, falsify the derived indication.
Solutions which are known for suppressing these systematic ranging errors involve the use of additional gradient systems in suitable arrangement with the original gradient ranging system (see U.S. Pat. No. 3,588,797 and U.S. Pat. No. 3,496,527 ). While theoretically such a solution should present a display with few errors for the desired direction of impingement, in practice the technical realization is both complicated and expensive. Additionally, due to the considerable increase in necessary equipment for the additional gradient system, there results an increase in the possibilities for error in the total operation of the system. Such a system would moreover be larger and also would have a higher weight.